Traditionally, dental wedges have been primarily used to reduce the incidence of excessive restorative material being pushed between the restoration “formwork” (or the “matrix band” as it is known in dental parlance) and the edge of the tooth in the region of the gum in between the teeth. Such protrusions . . . “overhangs” as they are known, cause floss to snag, and/or fray, cause bacteria and food and plaque to accumulate under the ledge, and can lead to periodontal disease and bone loss, plus increase the chances of future decay. Wedges also serve the dual purpose of stabilising the matrix band. This is especially important when a sectional matrix style of band is used as opposed to the circular toffelmire, sequland or auto matrix type band, which get a grip on the tooth by virtue of their 360° locking on, clamping action, as opposed to the limited 45 degree slice of the tooth the sectional matrix band typically sits next to.
Wedges were nearly always made of timber or wood (often sycamore) but in recent decades there has been a trend to make them from polymer materials, with varying degrees of success. Wedges were always made from flexible, moldable materials in order to adapt to the variable contours and space sizes between the teeth, but were never generally designed to provide substantial springback force when compressed, rather they were usually only able to flex to adapt, not to push back. As a result, virtually all wedges on the market need to be either used with additional equipment, or tightened on multiple occasions.
Wedges made of wood have the disadvantage that they have very little resilience or spring back power because they need to be stiff enough to push into the gap between the teeth at high force without buckling. Although they worked quite well to adapt to the curvature of the teeth, [except in furcations] and they hold the matrix band tightly against the proximal surfaces of that portion of the tooth apical to the edge of the cavity, because of their lack of resilience, they often resulted in poor quality tooth separation and thus poor quality contact points when the matrix band was removed. This is because removal of the matrix band creates a gap equal to the thickness of the band, and it is necessary to separate the teeth within their semi flexible and visco elastic tissue matrix during the course of the restorative procedure before the filling is hardened, at least by the thickness of the matrix band, so that the teeth touch firmly with no inter proximal gap once the band is removed.
This was not a problem in the past but now is due to the increasing use of composite resin. Composite resin restorations differ from other restorations like amalgams in that the lateral force applied by the restorative material during the condensation and packing of the filling phase is far less. As a result of this there is less lateral pressure put on the matrix band [like formwork] and far less separation created between the adjacent teeth, such that when the matrix band is removed composite restorations typically have the above mentioned gap, which typically is just wide enough to allow meat fibres and fine fibres from vegetables such a celery to enter the gap, especially during the high forces of mastication. Such food fibres, especially meat, often contain rubbery elastin, and when forced in under active biting pressure they effectively jam an elastomeric fibre in the gap under pressure, which in turn applies a slight expansive orthodontic like force to the gap. The adjacent teeth are thus pushed apart even further in the subsequent hours and days . . . thus causing the gap to become wider. Hence a viscous circle develops and the gap enlarges to receive even more food, usually up to about a self limiting but highly irritating/damaging width of about 0.8 mm-0.5 mm, and the patient not only gets an immediate uncomfortable, very annoying and irritating problem, but probably gum disease and decay in subsequent years from the impacted food.
As more of the world's dentists turn away from unsightly and mercury containing metallic amalgam, and use composite resin based restoratives for their primary restorative material, so this problem will increase, especially in third world countries where contact pressure may be seen as an optional peripheral refinement, not commercially justified given the lower fee level and time allowed, and a minor issue compared to the main concern of getting decay out and a filling of any kind into the hole. Even in sophisticated western markets it has been reported that as many as 60% of fillings done in composite [white] material result in food traps. [CRA survey] In the period prior to 1990 when the predominant restorative material throughout the world was metal amalgam, this was not such a large problem because amalgam condensation created such high lateral packing pressure it separated the teeth sufficiently so that on removal of the matrix the contact point was sufficiently tight so as not to routinely cause this food impaction problem.
Food packing between teeth however will soon manifest its serious side to those dentists new to composite, who wrongly assume that composite is the same as amalgam in outcome. Food trapping can cause devastating consequences for the patient with time. The bone loss caused by such food packing is usually irreversible and any decay caused by such food packing is usually at a point deep down next to the gum and often well below the gum at the bone level, where it is harder to restore, and where the tooth surface tapers in close to the pulp, or nerve. The nerve is much closer to the encroaching decay than with the usual interproximal and occlusal decay. This fact, combined with the generous nutrient supply from the trapped food to the bacteria making the decay, can cause the decay to start and advance quickly to the nerve, and for it to be infected and destroyed in an alarmingly short time. A dead nerve, apart from being painful, requires expensive root canal therapy, then a crown, but the margins of such crown have to be placed in a compromised sub gingival position right in the most difficult area for the patient to maintain in a plaque free state, (interproximally) and so the chances of periodontal disease and secondary caries increase around this crown. A second crown may be impossible to do because of the unrestorable nature of the sub gingival defect, leading to extraction of the tooth, and the need for an implant or denture or bridge, each with their own set of new risk factors. Thus it can be seen that a series and a lifetime of problems can potentially flow from the simple misadventure of a poorly executed composite resin restoration which results in an open or light contact point pressure with subsequent food trapping.
As a result of the inadequacy of wooden wedges to provide sufficient rebound effect and insufficient separating power, and as a result of the inadequacy of all the existing polymeric wedge wood substitutes to provide adequate separating power, a large industry has developed around the concept of providing separation between the teeth with other devices during the course of the restorative procedure. Instruments such as contact-pro have been used internally within the cavity to lever the teeth apart, and a large section of the general dental community now rely on the provision of metal rings with two legs, with trade names such as Compositite, palodent bitine rings, Garrison rings, Vrings etc to squeeze into the embrasure space between the teeth such that the vectors of force created by the squeezing ring legs apply a separating force between the teeth at the point where the restoration is likely to be placed. The use of these rings, although moderately successful in terms of outcome is somewhat unpredictable in terms of contact point pressure due to variabilities in tooth morphology, the extent of the caries and the amount and shape of the remaining tooth to engage, and the variable geometries and vectors of force that result. Also, use of the rings system is an extra step the clinician needs to take, unlike the current invention, which seeks to stabilise the matrix band, stop overhangs, and separate the teeth adequately at the same time. Also, often these rings are impossible or very difficult to use due to inadequate amounts of tooth structure to support their position on either side of the filling, unlike separation obtained internally within in the filling (eg “contact pro” and other instruments) or via the current invention.
The above rings can also become unstable and ‘ping’ off in the mouth and go down the throat and cause an inhalation hazard or swallowing hazard. They also still require the use of wedges anyway to stop overhangs and/or to stabilise the sectional matrix band.
Prior wedges are generally made triangular in cross section and made with excessive bulk and especially excessive vertical dimensions at the apex of this triangle that in the opinion of the patent author cause the wedges to interfere with and intrude upon the correct shape desired from the filling. They become intrusive into the desirable contour lines of the filling and distort the smooth flowing form of the matrix band and compromise the operator's ability to get a broad contact point and anatomically correct emergence profile. As a result many restorations have large embrasure spaces, causing more food to become lodged between the teeth by lateral placement during eating, and also causing the contact point anatomy to be more of a point contact at the occlusal surface, which is well known in the dental profession to be less able to resist food impaction than a broad area contact point further toward the gingival margin.
Also the cross sectional shape of most dental wedges is usually triangular or square at the point where they are held by the pliers or tweezers that are used to place and align and drive them into the interproximal space. Most dental wedge holding devices have opposing flat surfaces, which do not allow stable grasping of triangular or square surfaces except at certain discrete angles, and thus limit the flexibility and ease of use. Not only do most wedges not have the ability to be easily orientated 360 degrees, but they also mostly cannot be easily be orientated in the two other planes due to the shape they are made in, and thus they are less comfortable to place, requiring compensatory wrist movement, and not as easy to align so as to be in the ideal trajectory for the interproximal space. The use of the spherical ball at the attachment point is lacking and is designed to overcome this problem.